Apparatus for grinding drills



July 23, 1968 A, E, AHLSTROM 3,393,477

APPARATUS FOR GRINDING DRILLS Filed June 14, 1965 5 Sheets-Sheet l Fig.7

INVENTOR Qua" g m July 23, 1968 A. E. AHLSTRGM 3,393,477

APPARATUS FOR GRINDING DRILLS Filed June 14, 1965 5 Sheets-Sheet 2 INVENTOR BY M y 23, 1968 A. E. AHLSTRGM 3,393,477

APPARATUS FOR GRINDING DRILLS Filed June 14, 1965 5 Sheets-Sheet 5 INVENTOR July 23, 1968 A. E. AHLSTRUM 3,393,477

APPARATUS FOR GRINDING DRILLS 5 Sheets-Sheet 4 Filed June 14, 1965 INVENTOR aeamgaimm BY W14 July 23, 1968 A. L G 3,393,477

APPARATUS FOR GRINDING DRILLS Filed June 14, 1965 5 Sheets-Sheet 5 INVENTOR 6 MM United States Patent 3,393,477 APPARATUS FOR GRINDING DRILLS Allan Eugen Ahlstriim, Sloinge, Sweden Filed June 14, 1965, Ser. No. 463,593 Claims priority, application Sweden, Mar. 4, 1965, 2,792/ 65 3 Claims. (Cl. 51-241) ABSTRACT OF THE DISCLOSURE The invention is a grinding apparatus wherein a rotating twist =drill drives a rotary carriage or rotor carrying a grinder and its mounting shaft, both with a housing. The shaft of the grinder is swingable laterally with respect to the axis of the drill from grinding position to nonengag-ing position. Idler coupling means are provided between the drill and the carriage so that the grinder may be swung into grinding position, according to the number of cutting edges present on the drill during relative rotation of the drill and rotor. The grinder is also mounted so as to be slightly tilted so that grinding means on the carriage and grinder enable the grinder to grind with proper clearance or lip relief angle. In this manner successive cutting edges of the drill are ground with only one grinder. No adverse effects from centrifugal force are noted.

The invention will now be elucidated with reference had to the accompanying drawings. In the drawings:

FIG. 1 shows a vertical longitudinal section through the grinding apparatus according to the invention, showing the grinding disk during the grinding operation,

FIG. 2 shows a similar section but with the grinding disk swung away and out of contact with the drill,

FIG. 3 shows a vertical section through the portion of the grinding disk rotor at which portion the carrying housing of the grinding disk and the devices for its swinging are situated,

FIG. 4 is a side elevation of the portion shown in FIG. 3,

FIG. 5 shows the same portion seen from the left according to FIG. 4,

FIG. 6 shows the same portion from the right according to FIG. 4,

FIG. 7 is a plan view of the same portion,

FIG. 8 shows on a reduced scale a plan view of the grinding apparatus,

FIG. 9 shows from below (in the direction of the arrow IXIX in FIG. 1) a cam disk included in the apparatus,

FIG. 10 shows from below (in the direction of the arrow XX in FIG. 1) the devices for swinging the carrying housing of the grinding disk shaft and for supporting the cutting end of the drill during the rotating of the drill for the grinding of the subsequent edge,

FIGS. 11 and 12 are similar views as FIG. 10 'but showing these devices in different positions,

FIG. 13 shows on the same scale as in FIGS. 1 and 2 a plan view of the central portion of the grinding apparatus,

FIG. 14 shows a vertical section through this portion with the idle coupling of the apparatus,

FIGS. 15 and 16 are partly out side elevations seen from the right in FIG. 14 of the idling coupling in a driving position and in idling position,

FIG. 17 shows in a reduced scale a plan view of the rotor of the apparatus with the idling coupling, and

FIG. 18 is an end elevation of the operative end of the twist drill.

The twist drill 1 shown on the drawings is assumed to be clamped in the chuck of a post drill machine (not shown). The cutting end of the twisted drill 1 is provided with two cutting edges 2, 3 (FIG. 18) and two helically extending chip channels 4.

The main portions of the grinding apparatus are enclosed in a housing 6 of cylindrical shape for being held in one hand during use and provided with apertures 5 in the side walls and having a top 41 and a bottom 10. In the interior of the housing 6, having the shape of a box, there is mounted for rotation about the vertical central axis a rotor, generally designated at its lower part by the legend 7, and is, in a manner later described, driven by the drill 1. This rotor 7 is 'bearingly mounted on the one hand by an axial support trunnion 8 on one end of the rotor 7, said trunnion engaging in a guiding sleeve 9 on the bottom 10 of the housing 6, and on the other hand by means of a hub 11 carrying the upper, sleeve-shaped, portion 12 of the rotor. In this upper portion 12 there is journalled a sleeve 13 provided with a clamping chuck or a guiding and clamping sleeve 14 fitting the drill 1 in question. Between the sleeve 13 and the rotor 7 there is arranged a coupling 15 to be de scribed in detail in the following.

The grinding disk 16, arranged in the interior of the rotor 7 is fast on the inner end of a horizontal shaft 17 journalled in a carrying housing 18. This housing 18 is tiltably (FIG. 4) mounted on two carrying trunnions 19, situated below the shaft 17 and extending perpendicularly to the vertical plane of this shaft, on a frame-like stand 20 which is journalled in the rotor 7 to turn about an axis parallel to the axis of rotation of the rotor and thus also the axis of rotation of the twist drill 1. The grinding disk shaft 17 is driven via conical gears 21, 22 and an intermediate shaft 23 carrying on its lower end a gear wheel 24 which cooperates with a stationary ratcheted disk 25 near the bottom 10 of the housing 6. Between a bracket 26 (FIGS. 3 and 4) extending inwardly from the stand 20 and a stud 27 extending downwardly from the carrying housing 18 there is inserted a helical compression spring 28 by means of which the inner end of the carrying housing and thus also the shaft 17 and the grinding disk 16 tend to become tilted to elevated position for the disk to engage the drill 1. This tiling movement upwards is limited by means of an abutment 29, which during the turning of the stand 20 relative to the rotor, slides against the guiding rule 30 in the interior of the rotor 7. The lower edge 31 of this guiding rule is sloped somewhat in such a way that during the swinging of the carrying housing in lateral direction the housing is forced to follow a curved or an inclining movement path with the periphery of the grinding disk 16 in abutment against the cutting end 32 of the drill 1. Thus there is obtained the required clearance or lip relief angle of the cutting edges 2 and 3.

On the upper end of the stand 20 there is arranged a crank arm 33 having an outer end stud projecting upwardly into a downwardly opening circular groove 35 in a cam disk 36. The cam groove 35 is eccentrical in relation to the rotation axis of the rotor 7. The cam disk 36 is connected, as by a pin, to a gear wheel 37 and both are journalled on the sleeve-shaped upper portion 12 of the rotor 7. Above the gear wheel 37 there is secured fast on the rotor portion 12 a second gear wheel 38. The gear wheels 37 and 38 have the same division diameter but are provided with a difierent number of teeth. Preferably, the gear wheel 37 has about 160 teeth and the gear wheel 38 about teeth. The gear wheels 37, 38 cooperate with a common smaller gear wheel 39 which is journalled on a stationary tap 40 on the lower side of the upper portion 41 of the housing 6.

Upon rotation of the rotor 7 the cam disk 36, due to the different numbers of teeth of the gear wheels 37 and 38, will be turned slowly in relation to the rotor and, due to the fact that the cam groove 35 is arranged eccentrically, the stand 20 will by means of the crank 33, 34 turn and thereby cause a swinging of the grinding disk 16 from its central position in the rotor 7 below the cutting end 32 of the drill 1 away from this end and back to its initial position. During this swinging movement the rotor 7 will have undergone a considerable number of revolutions, and the grinding disk 16 with its shaft will have rotated much faster still. Of course the speed of rotation of the grinding disk depends on the gearing ratio such as 24, 25 and 21, 22.

Below the upper disk-shaped portion 42 of the rotor 7 a drill channel engagement arm 44 is journalled on a short vertical shaft 43 fast on the upper end of the frame-like stand 20 (FIGS. -12). The arm 44 has a swingable end 45 shaped to engage in a channel of the drill and thus hold the drill in correct position. The arm 44 and end 45 are swung in one direction by means of a hook shaped dog 46 and in the other direction by an abutment 47', both on an actuating arm 47 secured on the short shaft 43. There is a certain amount of lost angular motion between the arms 44 and 47 as shown in FIGS. 10, 11 and 12 so that the outer end of arm 47 can remain under the pointed end of the drill and receive its thrust during rotation of the drill to bring a different cutting edge into position to be ground. This rotating shall be explained in detail in the following in connection with the explanation of the coupling of the apparatus.

On the upper portion 12 of the rotor 7 (FIGS. l4l7), which is journalled in the hub part 11, is provided with a radial pivot stud 48 carrying a latch lever 49 having camming and abutment arms 52 and 53, respectively. The lever 49 is biased to a clockwise position as shown in FIG. 15 by a spring 50. In this position the abutment arm 53 can engage against end wall abutments 54 of a pair of diametrically opposite recesses 58 in a lower flange portion 55 on the sleeve 13, with the latch arm 52 riding with a rounded surface 51 engaging the under face '56 of the central portion 56 of the cam 34. Upon rotation of the sleeve 13 and its flange 55 in the direction of the arrow 157, one of the wall abutments 54 drives the latch and with it the sleeve 12, to rotate the rotor 7 as a whole. The lower face 56 of the central portion 56 of the cam member 36 is provided with a downwardly extending hump 57 to engage on and depress the latch arm 51 as shown in FIG. 16 and so permit rotation of the inner sleeve 13 relative to the rotor sleeve 12.

But as explained previously, the rotor 7 and the cam member 36 do not rotate at the same speed due to the difference in toothing of the gear wheels 37 and 38. Hence for every engagement of the cam hump 57 on the latch arm 52 there is an unlatching of the coupling 15 between the inner sleeve 13 and the rotor 7 and the unlatching or uncoupling can occur at almost any position the rotor assumes in the housing case 5, since relative positions of the cam member 36 and the rotor determine the uncoupling. The same relative position of cam 36 and sleeve 13 determine the swing of the framelike stand and consequently the swing of the grinder 16 as well as thrust or support piece 47 and the -feeler 45. Upon uncoupling by latch, the inner sleeve 13 with the drill becomes free to rotate relative to the rotor with the end of the arm 47 receiving thrust of the drill during half a revolution of the drill. However as soon as the cam hump 57 leaves the arm 52 the latch is turned by the spring 50 so as to engage the corresponding abutment in the diametrically opposite recess 58. The sleeve 13 is then automatically again coupled to the rotor 7 which then is driven by means of the drill 1. For each complete revolution of the cam disk 36 in relation to the rotor 7 there is thus caused a freeing and a turning of the drill half a revolution in relation to the rotor 7.

Thus, it is understood from the aforegoing that by means of a grinding apparatus according to the invention it is possible to grind a drill clamped in the chuck of a drilling machine without any need of removing the drill from the chuck. Upon finished grinding of one of the cutting edges, e.g. the one denoted 2, so that the required clearance behind the cutting edge is obtained, the drill is allowed to turn half a revolution in relation to the rotor 7 of the apparatus whereupon the grinding disk 16 is swung asideand thereupon the grinding disk disk 16 is automatically swung back to its operative position during the grinding of the second cutting edge 3. The course of events can then be repeated any desired number of times until the drill has been completely ground.

Due to the fact that the carrying housing 18 with the grinding disk 16 and the shaft 17 of the latter is carried on the trunnions 19 below the shaft 17 there is created by the centrifugal force at the speedy rotation of the rotor 7 a moment of rotation tending to swing the carrying housing 18 in counter-clockwise direction according to FIG. 1 in such a way that the grinding disk 16 is urged against end 32 of the drill. This abutment force thus contributes to an increased grinding effect.

On the inner end of the shaft 17 there is arranged a ring of flanges or the like 59 which in common serve as a fan for blowing the chips formed out through the apertures 5 in the housing 6.

About the carrying trunnion 8 there is above the guiding sleeve 9 inserted a filter ring 60 soaked with oil, said ring on the one hand greasing this lower bearing and on the other hand preventing an entering of the chips into the bearing.

The invention has been described in the aforegoing for purposes of illustration only and it is not intended to be limited by this description or otherwise except as defined in the appended claims. Thus, the different parts of the grinding apparatus can be modified in many ways without departure from the scope of the claims. The force transmission to the grinding disk 16 can be carried out otherwise than described in the aforegoing and shown in the drawings.

The invention has been described in the aforegoing as carried into effect for the grinding of a twist drill with two cutting edges 2 and 3. In case the grinding apparatus is to be used for grinding drills having more than two cutting edges, the coupling must be shaped in accordance thereto. Generally, the coupling must be shaped in such a way that the sleeve 13 with the drill 1, each time the cam 57 (or any of the cams) passes the lever 52, is freed from the rotor and allowed to rotate a part of a revolution corresponding to the number of cutting edges of the drill.

What I claim is:

1. A grinding apparatus for a twist drill comprising a housing for being held substantially stationary and having upper and lower walls, an axially vertical rotor within the housing and having an upper coaxial sleeve portion mounted for rotation on the upper wall and rotatably receiving a coaxial chuck means for, in turn, receiving the fluted end portion of a drill to be sharpened; latchlike coupling means for normally coupling the chuck means to the rotor; a grinder disc within the housing for engaging the end of the drill and mounted on a generally horizontal grinder spindle normally about radial to the rotor axis; a bearing member for carrying the spindle and mounted on the rotor for tilting and for swinging about an axis transverse to the spindle and parallel with that of the rotor; gear means for converting rotation of the rotor relative to the housing to higher speed rotation of the grinder spindle; a cam member concentric with and about the sleeve portion and geared with the chuck means to turn at a lower speed than the latter, and having a bump to disengage said coupling means between the chuck means and the rotor to allow the drill to turn relative to the rotor, said cam member having a downwardly open eccentric channel; a bell crank on the spindle bearing member and engaging in said channel for swinging the member about its axis transverse to the spindle upon relative turning of the rotor and cam memher, said bearing member having a spring for tilting the bearing member, spindle and disc upwardly for the latter to normally engage the drill; cam means on the bearing member and rotor for drawing the disc downwardly from the drill when the bell crank swings the bearing member; respective guiding and supporting arms on the bell crank and turnable about said transverse axis of the bearing member, the former having a free end to engage in a chip channel of the drill for steadying same in the chuck when the drill is ground, and the latter for supporting the drill when the disc is swung away, the supporting arm being turntable with the bell crank; lost motion means for turning the guiding arm by the support arm; the timing of the cam member and the bell crank with respect to the supporting arm being such that when the bump of the cam member disengages said coupling means to allow the chuck means to rotate with respect to the rotor, the guiding arm and disc will swing about said transverse axis and the guiding arm be free to move to the opposite flute of the drill.

2. A grinding apparatus as claimed in claim 1, said rotor including a stand turnable about said transverse axis and carrying the bearing member, and said bell-crank being on the upper end of the stand.

3. A grinding apparatus as claimed in claim 1, said cam member and cam means being shaped to provide clearance cutting on the end of the drill.

References Cited UNITED STATES PATENTS 2,017,532 10/1935 Elter 51-120 X 2,177,644 10/1939 Finke 51120 HAROLD D. WHITEHEAD, Primary Examiner. 

